diff --git a/briar-api/src/main/java/org/briarproject/briar/api/attachment/MediaConstants.java b/briar-api/src/main/java/org/briarproject/briar/api/attachment/MediaConstants.java
index 7c13575c3..90c851630 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/attachment/MediaConstants.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/attachment/MediaConstants.java
@@ -11,7 +11,7 @@ public interface MediaConstants {
 	/**
 	 * The maximum length of an attachment's content type in UTF-8 bytes.
 	 */
-	int MAX_CONTENT_TYPE_BYTES = 50;
+	int MAX_CONTENT_TYPE_BYTES = 80;
 
 	/**
 	 * The maximum allowed size of image attachments.
diff --git a/briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingConstants.java b/briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingConstants.java
index 4a87775e0..c5594fa3f 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingConstants.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingConstants.java
@@ -7,7 +7,17 @@ public interface MessagingConstants {
 	/**
 	 * The maximum length of a private message's text in UTF-8 bytes.
 	 */
-	int MAX_PRIVATE_MESSAGE_TEXT_LENGTH = MAX_MESSAGE_BODY_LENGTH - 1024;
+	int MAX_PRIVATE_MESSAGE_TEXT_LENGTH = MAX_MESSAGE_BODY_LENGTH - 2048;
+
+	/**
+	 * The maximum length of an incoming private message's text in UTF-8 bytes.
+	 * This is higher than MAX_PRIVATE_MESSAGE_TEXT_LENGTH for compatibility
+	 * with older peers.
+	 * <p>
+	 * TODO: Remove after a reasonable migration period (added 2021-03-12).
+	 */
+	int MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH =
+			MAX_MESSAGE_BODY_LENGTH - 1024;
 
 	/**
 	 * The maximum number of attachments per private message.
diff --git a/briar-core/src/main/java/org/briarproject/briar/messaging/PrivateMessageValidator.java b/briar-core/src/main/java/org/briarproject/briar/messaging/PrivateMessageValidator.java
index af735c73c..8a1541277 100644
--- a/briar-core/src/main/java/org/briarproject/briar/messaging/PrivateMessageValidator.java
+++ b/briar-core/src/main/java/org/briarproject/briar/messaging/PrivateMessageValidator.java
@@ -32,7 +32,7 @@ import static org.briarproject.briar.api.attachment.MediaConstants.MAX_CONTENT_T
 import static org.briarproject.briar.api.attachment.MediaConstants.MSG_KEY_CONTENT_TYPE;
 import static org.briarproject.briar.api.attachment.MediaConstants.MSG_KEY_DESCRIPTOR_LENGTH;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_ATTACHMENTS_PER_MESSAGE;
-import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_TEXT_LENGTH;
+import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH;
 import static org.briarproject.briar.client.MessageTrackerConstants.MSG_KEY_READ;
 import static org.briarproject.briar.messaging.MessageTypes.ATTACHMENT;
 import static org.briarproject.briar.messaging.MessageTypes.PRIVATE_MESSAGE;
@@ -103,7 +103,7 @@ class PrivateMessageValidator implements MessageValidator {
 		// Private message text
 		checkSize(body, 1);
 		String text = body.getString(0);
-		checkLength(text, 0, MAX_PRIVATE_MESSAGE_TEXT_LENGTH);
+		checkLength(text, 0, MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH);
 		// Return the metadata
 		BdfDictionary meta = new BdfDictionary();
 		meta.put(MSG_KEY_TIMESTAMP, m.getTimestamp());
@@ -117,7 +117,7 @@ class PrivateMessageValidator implements MessageValidator {
 		// Message type, optional private message text, attachment headers
 		checkSize(body, 3);
 		String text = body.getOptionalString(1);
-		checkLength(text, 0, MAX_PRIVATE_MESSAGE_TEXT_LENGTH);
+		checkLength(text, 0, MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH);
 		BdfList headers = body.getList(2);
 		if (text == null) checkSize(headers, 1, MAX_ATTACHMENTS_PER_MESSAGE);
 		else checkSize(headers, 0, MAX_ATTACHMENTS_PER_MESSAGE);
diff --git a/briar-core/src/test/java/org/briarproject/briar/messaging/PrivateMessageValidatorTest.java b/briar-core/src/test/java/org/briarproject/briar/messaging/PrivateMessageValidatorTest.java
index 74ed605d3..cc42c0c87 100644
--- a/briar-core/src/test/java/org/briarproject/briar/messaging/PrivateMessageValidatorTest.java
+++ b/briar-core/src/test/java/org/briarproject/briar/messaging/PrivateMessageValidatorTest.java
@@ -31,7 +31,7 @@ import static org.briarproject.briar.api.attachment.MediaConstants.MAX_CONTENT_T
 import static org.briarproject.briar.api.attachment.MediaConstants.MSG_KEY_CONTENT_TYPE;
 import static org.briarproject.briar.api.attachment.MediaConstants.MSG_KEY_DESCRIPTOR_LENGTH;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_ATTACHMENTS_PER_MESSAGE;
-import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_TEXT_LENGTH;
+import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH;
 import static org.briarproject.briar.client.MessageTrackerConstants.MSG_KEY_READ;
 import static org.briarproject.briar.messaging.MessageTypes.ATTACHMENT;
 import static org.briarproject.briar.messaging.MessageTypes.PRIVATE_MESSAGE;
@@ -55,7 +55,7 @@ public class PrivateMessageValidatorTest extends BrambleMockTestCase {
 	private final Message message = getMessage(group.getId());
 	private final long now = message.getTimestamp() + 1000;
 	private final String text =
-			getRandomString(MAX_PRIVATE_MESSAGE_TEXT_LENGTH);
+			getRandomString(MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH);
 	private final BdfList attachmentHeader = getAttachmentHeader();
 	private final MessageId attachmentId = new MessageId(getRandomId());
 	private final String contentType = getRandomString(MAX_CONTENT_TYPE_BYTES);
@@ -132,7 +132,7 @@ public class PrivateMessageValidatorTest extends BrambleMockTestCase {
 	@Test(expected = InvalidMessageException.class)
 	public void testRejectsTooLongTextForLegacyMessage() throws Exception {
 		String invalidText =
-				getRandomString(MAX_PRIVATE_MESSAGE_TEXT_LENGTH + 1);
+				getRandomString(MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH + 1);
 
 		testRejectsLegacyMessage(BdfList.of(invalidText));
 	}
@@ -190,7 +190,7 @@ public class PrivateMessageValidatorTest extends BrambleMockTestCase {
 	@Test(expected = InvalidMessageException.class)
 	public void testRejectsTooLongTextForPrivateMessage() throws Exception {
 		String invalidText =
-				getRandomString(MAX_PRIVATE_MESSAGE_TEXT_LENGTH + 1);
+				getRandomString(MAX_PRIVATE_MESSAGE_INCOMING_TEXT_LENGTH + 1);
 
 		testRejectsPrivateMessage(
 				BdfList.of(PRIVATE_MESSAGE, invalidText, new BdfList()));